Reconfigurable electrode apparatus for diagnosis of arrhythmias

Example apparatuses disclosed herein are generally usable with catheter-based systems to measure or provide electrical signals within the heart and surrounding vasculature. Example apparatuses generally include an end effector with one or more spines that can rotate about a longitudinal axis such that the spines are aligned in a plane in a first configuration and the one or more spines are rotated out of the plane in a second configuration. The end effector can include features which provide improved and/or alternative diagnostic or treatment options compared to existing end effectors. In some example treatments utilizing some example apparatuses presented herein, an end effector can map a wall within the heart in the first configuration and a lumen of a vein in the second configuration.